Pulsed laser deposition is a method of applying a film to the surface of a substrate material. Often the film is specified to be very thin. An example of an application of pulsed laser deposition is the deposition of superconducting films on various substrates. The desired thickness of these films is in the range of approximately 100 to 50,000 angstroms.
During the pulsed laser deposition process, the substrate is placed in a vacuum chamber together with a solid mass of target material. This target material is often a composition of materials, which will undergo a chemical reaction during the deposition process, thereby forming the desired deposit material. A high power laser has its beam incident on the target material. The laser vaporizes the target material, producing a plume. The plume diffuses toward the substrate and is deposited on the surface of the substrate.
A problem with pulsed laser deposition is that it is difficult to reliably and consistently achieve a desired morphology, physico-chemical structure, and thickness of the deposited film. Other important properties that vary because of inadequate process control are current-carrying capability, surface roughness, and response to radiation. The lack of process control is exacerbated as the size of the surface to be coated increases.
As an example of poor process control, in the case of a superconducting film of yttrium barium copper oxide, manufacturing inadequacies account for a wide variation in critical temperature. The best films have a critical temperature of 92 K, but in actuality, most films have a lower critical temperature.